vnd storage on NFS -> panic

[Stephen Borrill <netbsd%precedence.co.uk@localhost>]

What is the general consensus on best practice for shared storage between 
dom0s? i.e. I would like bring up the domU on a different machine if 
required.

I have NetBSD 5.0_STABLE dom0s (a mixture of i386 PAE and amd64) with Xen 
3.3.2. I recall that there are issues with sparse vnd files on ffs, but 
thought sparse files on NFS was OK. I created a 10G sparse file on NFS and 
then attempted to use that for a NetBSD i386 domU (amd64 dom0 with 8GB RAM 
and wm(4) as network cards). On the first domU disk write (disklabel from 
sysinst), the dom0 panicked:

panic: kernel diagnostic assertion "pg != NULL" failed: file 
"/usr/src/5.0/sys/uvm/uvm_pager.c", line 524

--
Stephen